Heat exchanger

ABSTRACT

A compact heat exchanger and/or fluid mixing means comprises a bonded stack of plates, the stack comprising at least one group of plates, the group comprising one or more perforated plates ( 10 ) sandwiched between a pair of primary separator plates ( 40, 62, 64 ), characterised in that each perforated plate ( 10 ) has perforations ( 14 ) arranged in rows across the plate in a first direction, with a land ( 16 ) between each adjacent pair of perforations ( 14 ) in a row and with ribs ( 18 ) between adjacent rows, the lands ( 16 ) forming barriers to flow in a first direction across the plate and the ribs ( 18 ) forming barriers to flow in a second direction across the plate, the second direction being normal to the first direction, the ribs ( 18 ) having vents ( 20 ) through a portion of their thickness, the vents ( 20 ) extending from one side of a rib ( 18 ) to the other side in the second direction, whereby flow channels are provided through the vents ( 20 ) and the flow channels lying between each adjacent pair of lands ( 16 ) provide a flow passage to cross the plates in the second direction, the passageways in the group of plates being separated from passageways in any adjacent group of plates by one of the separator plates ( 40 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/937,666 filed on Sep. 26, 2001 which in turn claims priorityto foreign applications for patent, Great Britain Serial No. 9907032.8,filed Mar. 27, 1999, Great Britain Serial No. 9914364.6, filed Jun. 19,1999, and international patent application serial number PCT/GB00/00631filed on Feb. 24, 2000 which are hereby incorporated by reference.

BACKGROUND OF INVENTION

[0002] This invention relates to a compact heat exchanger and/or fluidmixing means which incorporates a series of plates having apertureswhich define a plurality of passages through which fluid may flow.

[0003] Compact heat exchangers are characterised by their high “areadensity” which means that they have a high ratio of heat transfersurface to heat exchanger volume. Area density is typically greater than300 m²/m³ . and may be more than 700 m²/m³. Such heat exchangers aretypically used to cool (or heat) process fluids.

[0004] One well known but expensive to manufacture type of heatexchanger is the so-called tube and shell heat exchanger. Essentiallysuch heat exchangers consist of an exterior tubular shell through whichrun a number of longitudinally-extending smaller diameter tubes carryingone or more fluids. Other fluids, with which heat is to be exchanged,typically pass transversely across the heat exchanger such that heat isexchanged through the tube walls. A large number of tubes may be neededand they each have to be individually and accurately fixed/secured intoa header plate at each end of the shell. In each case holes need to bedrilled in the header plates very accurately to locate the tubes. Highquality tested tubing then needs to be assembled into the plates andbrazed or welded or mechanically-expanded into position. As the tubesare reduced in diameter to increase surfaces available for heat transferand hence performance/compactness, the more difficult and expensive suchconfigurations become to manufacture.

[0005] A second known type of heat exchanger is the so-called primaryplate/secondary plate type exchanger in which a stack of plates isassembled, the stack having primary plates which directly separate twodifferent fluid streams and secondary plates between adjacent primaryplates. The secondary plates act as fins which add to the strength ofstructure and may be provided with perforations to provide additionalflow paths for the fluids. The plates are usually bonded together bybrazing but this may have the disadvantage of affecting the physicalproperties of the plates in the brazed regions—or may introduce into thesystem, by means of the braze material, a potentially less satisfactorystructure in terms of strength and corrosion resistance. It has beenproposed to bond the plates together by diffusion bonding but asatisfactory construction that can withstand the high pressures involvedhas not been achieved and the fins may buckle during the bondingprocess.

SUMMARY OF THE INVENTION

[0006] It is an object of the present invention to provide an improvedconstruction of this second type of heat exchanger which can besatisfactorily made by, for example, diffusion bonding or by brazing. Italso aims to provide a heat exchanger construction which can also bereadily adapted for use as a fluid mixing means, e.g. it can be used asa chemical reactor in which fluids which are to react together aremixed. Thus, where a reaction is exothermic, the invention may provide ameans whereby the exothermic heat of reaction may be removed efficientlyor, alternatively, it may be used to supply heat to an endothermicreaction. The products of the invention are also useful as fuelreformers and gas clean-up units associated with fuel cell technology.

[0007] Accordingly the present invention provides a heat exchanger orfluid mixing means comprising a bonded stack of plates, the stackcomprising at least one group of plates, the group comprising one ormore perforated plates sandwiched between a pair of primary separatorplates, each perforated plate having perforations arranged in rowsacross the plate in a first direction, with a land between each adjacentpair of perforations in a row and with ribs between adjacent rows, thelands forming barriers to flow in the first direction across the plateand the ribs forming barriers to flow in a second direction across theplate, the second direction being normal to the first direction, theribs having vents through a portion of their thickness, the ventsextending from one side of a rib to the other side in the seconddirection, whereby flow channels are provided through the vents and theflow channels lying between each adjacent pair of lands provide a flowpassageway to cross the plates in the second direction, the passagewaysin the group of plates being separated from passageways in any adjacentgroup of plates by one of the separator plates.

[0008] Although the group of plates may in fact contain only oneperforated plate, there may be two or more perforated plates in thegroup of plates and in this embodiment adjacent perforated plates arealigned whereby the perforations of a row in one plate lie incorrespondence with those of adjacent plates so that the lands and ribsof the plates lie in correspondence respectively with each other.

[0009] The invention will be more particularly described below withreference to embodiments in which the, or each, group of plates containstwo or more perforated plates.

[0010] It will be appreciated that the flow passages can equally beprovided in the first direction instead of the second direction, i.e.the lands are effectively the ribs containing the vents and the ribs arethe lands.

[0011] The separator plates may be unperforated to provide completeseparation of the passageways of the respective groups of plates.Alternatively, the separator plates may contain holes positioned andsized to provide controlled mixing of the fluids in those passageways.Such a separator plate will be referred to below as a mixing plate.

[0012] As indicated above each group of perforated plates preferablycomprises at least two perforated plates but may contain three or moreadjacent perforated plates as desired. A stack may, for example,comprise two or more groups of perforated plates separated by separatorplates, each group containing two perforated plates having theirperforations aligned in rows.

[0013] The passageways across the plates preferably traverse across theplates once only from a first edge to a second edge. However, in analternative first specific embodiment, the passageways at one or bothplate edges may be turned, e.g. by an appropriate passagewayarrangement, through an angle whereby the passageway defined by thechannels continues in a different direction through the stack, e.g. inthe opposite direction so as to return from the second edge to the firstedge.

[0014] In a second specific embodiment two or more separate passagewaysare provided across a group of plates whereby streams of differentfluids may flow parallel to each other in the same layer provided bysaid group of plates. This embodiment can provide improved temperatureprofiles across the plates and reduced thermal stress.

[0015] Because the plates are stacked with the perforated plates of eachgroup aligned with their perforations in rows, it will be appreciatedthat the solid regions (i.e. ribs and lands) of those plates between therows of perforations and between the perforations are also aligned inrows. As the perforated plates, therefore, are stacked one above eachother, the ribs and the lands are aligned through the stack and thisprovides strength through the assembled stack whereby the pressuresgenerated in the bonding process can be withstood. The invention,therefore, provides a stack structure that can be bonded without therisk of the fins of the secondary plates collapsing under the pressuresgenerated. The fins also provide the means of withstanding internalpressures in the operating streams. The rows of ribs and of lands mayrun in parallel lines across the plates but this is not essential.

[0016] The perforations may be of any desired shape but are preferablyelongated slots.

[0017] The plates may be rectangular, square or circular for example orof any other preferred shape.

[0018] Where the plates are square or rectangular, each row of slots mayextend from a first edge of the plate parallel to a second edge of theplate and for substantially the whole length of that second edge. Itwill be appreciated that a substantially unperforated edge or borderwill normally be required around the perimeter of the major faces of theplate to enable the plates of the stack to be bonded together and toprovide pressure containment for the stream or streams. However, acompletely unperforated border is not essential and slots in the bordermay be required for inlet and outlet means, for example. A plurality ofrows of slots may, therefore, extend across the plate from the firstedge to the opposite, third, edge.

[0019] Where the plates are circular the rows and passageways may extendfrom the outer perimeter as a segment of the circle towards the centre.

[0020] In one particular arrangement of the aforesaid second embodiment,a stack may be built up of one or more similar groups of plates, eachgroup comprising an upper and a lower unperforated separator plate, amultipassageway input layer in contact with one separator plate and acorresponding multi-passageway output layer in contact with the otherseparator plate, a centrally-disposed layer having at least onepassageway for a first fluid and two or more transfer passageways for afluid from each passageway of the input layer, a first auxiliaryperforated plate lying between the input layer and thecentrally-disposed layer and a second auxiliary perforated plate lyingbetween the output layer and the centrally-disposed layer, theperforations in the first auxiliary perforated plate being positioned totransfer fluid from each passageway of the input layer to thecorresponding transfer passageways in the centrally-disposed layer andthe perforations in the second auxiliary perforated plate beingpositioned to transfer fluid from the transfer passageways to thecorresponding passageways of the output layer. The centrally-disposedlayer can conveniently be formed of a plurality of main perforatedplates as described above, as can the input and output layers.

[0021] The perforations or slots are preferably photochemically etchedthrough the plates by known means, although spark erosion, punching orany other suitable means may be used, if desired.

[0022] The vents may be similarly formed and are preferably formed byphotochemical etching. The vents are conveniently formed in the ribs onone surface of the plate so as to extend partially into the thickness ofthe rib (i.e. the thickness of the plate.). They may for example be of adepth equal to about one half of the plate. However, it may beadvantageous to form vents in both surfaces of the plate, in which casethe vents in one surface should preferably be staggered from those inthe other surface.

[0023] For convenience the invention will hereafter be described withmore specific reference to vents in the ribs although it will beappreciated, as indicated above, that they may equally be formed in thelands rather than the ribs.

[0024] A stack of adjacent perforated plates has rows of lands and rowsof ribs. In the ribs between any adjacent pair of rows of lands therewill be a plurality of vents forming flow channels across the plates.These flow channels together form a flow passageway that is separatedfrom adjacent groups of flow channels, i.e. adjacent flow passageways,by the rows of lands. Thus each of the plurality of fluid channelsforming an individual passageway may pass through the stack without anycommunication with the channels of another passageway. No mixing offluid in those passageways can, therefore, take place and the stackfunctions purely as a heat exchanger with fluids at differenttemperatures passing through different groups of perforated plates orpassing through different passageways in the same group of perforatedplates.

[0025] In another embodiment of the invention there is providedintercommunication at selected positions between adjacent passageways.Thus cross-channels or cross vents may be etched or otherwise formed inthe lands of the plates to provide access between adjacent passageways.The cross vents may be formed at any desired position along thepassageways. Thus fluid flowing through separate passageways may beblended at prearranged positions on its journey through the passagewaysthrough the stack and this blending may be employed to ensure good fluiddistribution and to improve heat exchange capability. (It will beappreciated that where the vents are in the lands rather than the ribs,then the cross vents will be in the ribs rather than the lands.).

[0026] Alternatively or additionally, inlets for a further fluid may beprovided through the peripheral borders of the plates. Thus reactant maybe introduced and mixed via the peripheral border inlets whereby thestack may be employed as a chemical reactor.

[0027] In another embodiment the invention provides a stack in which afluid stream from one group of perforated plates may be injected into afluid stream in an adjacent group of perforated plates. Injection holesfor this purpose are provided in a mixing plate which separates the twogroups of perforated plates. So-called “process intensification” can beachieved by this means, and any reaction caused by the injection of afirst fluid into a second fluid can be controlled by the pressuredifferential between the two streams, the size, numbers and spacing ofthe injection holes and by sandwiching the second stream between thefirst stream and a coolant or heating stream, as appropriate.

[0028] The density of the slots, and hence of the ribs or fins betweeneach row of slots, may be varied, as required. Thus the number of slotsper unit width or per unit length of a plate may be arranged to suit anyparticular flow/pressure drop/distribution change requirements.

[0029] The vents in adjacent pairs of ribs are preferably offset fromeach other so that fluid flow across the plates is continually changingdirection in that it must follow a sinuous route. It will be appreciatedthat each time the flow passes through a vent, the flow area and hencevelocity changes resulting in turbulence and good heat transfer throughthe mass of the plates, albeit with associated pressure drops. Theskilled man of the art will, therefore, be able to design a wide varietyof heat exchanger characteristics and to optimise the desired effects.

[0030] The vents may be formed normal to the direction of the rib orthey may be angled through the rib so as to provide an increasedsideways component of movement. The vents may be tapered, especiallynarrowed in the direction of flow to their exit into a slot. Thus flowvelocity will increase as fluid enters a vent from a slot and willincrease further due to the tapering effect.

[0031] It will also be appreciated that the main flow direction acrossthe plates is through the vents and that flow normal to that direction,i.e. through any cross vents that are provided, will normally berestricted by the provision of fewer and/or smaller cross vents.

[0032] The rows of slots may extend linearly across the plate but thisis not essential and they may be arranged in other desired patterns,e.g. herringbone or chevron.

[0033] The plates may be provided at their edges with extensions, e.g.in the form of lugs to assist location of the plates in a stack. Suchlugs may be designed to be broken off after the stack has beenassembled, e.g. by etching partway through their thickness along a linewhere the lug joins the plate. Alternatively the extensions may fittogether in the stack to provide, e.g. one or more tanks on the sidefaces of the stack. Each extension may, for example, be in the form of aflat loop, e.g. of semi-circular profile, providing an aperture at theedge of the plate, the apertures of adjacent plates forming the volumeof the tank when the plates are stacked together. The loops may beattached to the plate not only at their ends but also across theaperture by means of narrow ligaments. The tanks so formed can each feedfluid, e.g. process fluid, coolant or reactant which is fed into thetanks, into the channels of one passageway. Thus a tank will becoterminous on the side of the stack with the height and width of thepassageway, i.e. a group of channels, to be fed. Where the stacks arepolygonal in plan, a tank may be provided on one or more of the sidefaces of the stack. Where the stacks are circular in plan, a number oftanks may be spaced around the perimeter as desired.

[0034] Plates used to form the products of the invention may also beprovided with a hole, e.g. disposed centrally through each plate,whereby a stack of the plates has a centrally-disposed discretepassageway for a fluid stream through the stack. To compensate for theloss of flow area where such a central hole is provided, it is possible,where the plate is provided with integral tank loops, to extend theplate outwardly between adjacent loops.

[0035] The plates of a stack are preferably of the same material and arepreferably thin sheets of metal, e.g. of 0.5 mm thickness or less. Thematerial is preferably stainless steel but other metals, e.g. aluminium,copper or titanium or alloys thereof, may be used.

[0036] Inlet and outlet headers or manifolds for the different fluidsmay be secured to the stack after bonding together of the stack platesor, alternatively, may be formed from integral features on the plates.

[0037] As indicated above, the components of a stack may be bondedtogether by diffusion bonding or by brazing. Diffusion bonding, wherepossible, may be preferred but, in the case of aluminium, which isdifficult to diffusion bond, brazing may be necessary. It is thenpreferable to clad the aluminium surfaces, e.g. by hot-roll pressurebonding, with a suitable brazing alloy, in order to achieve satisfactorybonding by the brazing technique, although other means to provide thebraze medium may be used, e.g. foil or vapour deposition.

[0038] The invention is particularly useful where it is desired to buildup a large heat exchanger by bonding side by side a number of heatexchanger units. Each unit can be provided by a stack of plates of theinvention. Each stack may, for illustration purposes only, be formed ofplates of, say, 300 mm width by 1200 mm length and of the desired heightdepending on the thickness and number of plates. Several stacks can beplaced side by side on a separator plate and then the assembly closed atthe top by another separator plate. If six stacks, for example, areutilised side by side, a heat exchanger of about 1800 mm flow length isachieved. All required lugs, mitre sections, spacers, etc. can be formedintegrally and built up from appropriate formations on each plate andall the stacks will be of the same height, being made up of identicalplates. Such an arrangement has significant advantages in themanufacture of, for example, “cryogenic” aluminium heat exchangers,which conventionally have to be built up of layers of corrugations withseparate side bars. Unless the height of the side bars relative to theheight of the corrugations is correct lack of uniformity andunsatisfactory brazing of the product may result.

[0039] It is known that chemical reactions can be catalysed inside astructure such as a heat exchanger by providing a deposit of catalyticmaterial in the internal passageways through which the fluid(s) to becatalysed are passed.

[0040] The perforated plates used in the present invention areparticularly useful in this respect as the surfaces of the ribs, landsand vents can receive a catalytic material coating of relatively modestthickness and the slots in the perforated plate can receive a muchthicker deposit of the catalytic material. Thus, for example, where thevents extend into the thickness of the ribs to a depth equal to aboutone half of the plate thickness, the catalyst deposit in the slots canbe of depth up to half the plate thickness without causing any blockageof the vents.

[0041] In a further embodiment of the invention is provided a heatexchanger/catalytic reactor having a plurality of passageways to containcatalytic material to promote a chemical reaction in fluid(s) to bepassed through those passageways, those passageways being separated byan intervening plate from a stack of one or more parallel perforatedplates having a vented rib structure according to the present invention.Thus the stack of plates separated by the intervening plate from theadjacent passageways, which later will be filled with catalyticmaterial, is formed from perforated plates, each having perforationsarranged in rows across the plate in a first direction, with a landbetween each adjacent pair of perforations in a row and with ribsbetween adjacent rows, the lands forming barriers to flow in the firstdirection across the plate and the ribs forming barriers to flow in asecond direction across the plate, the second direction being normal tothe first direction’, the ribs having vents through a portion of theirthickness, the vents extending from one side of a rib to the other sidein the second direction, whereby flow channels are provided through thevents and the flow channels lying between each adjacent pair of landsprovide a flow passage to cross the plates in the second direction.

[0042] Once the heat exchanger structure has been completed and tested,the catalytic material may be packed into its passageways. However, thepacking of the catalytic material will normally be completed immediatelyprior to the installation of the heat exchanger/reactor into its desireduse position.

[0043] The passageways to contain the catalytic material are preferablydefined between parallel ribs running the length of their plates toallow convenient introduction of the catalytic material and itssubsequent removal at the end of its life cycle. The passageways may beclosed off at one or both ends by a mesh to retain the catalyticmaterial.

[0044] By means of this further embodiment, heating or cooling can veryeffectively be provided for the chemical reaction by passing a heatingor cooling fluid through the stack of plates adjacent to the layerscontaining the catalyst. As indicated above, this structure causes suchtortuous flow and turbulence that very good heat transfer properties canbe achieved, especially with gaseous fluids. The catalysed reaction may,therefore, if exothermic, be effectively cooled by passage of a suitablecooling fluid, or if endothermic, may be heated and hence initiated orimproved by passage of a suitable heating fluid, through the stack.

[0045] This further embodiment may also be used in conjunction with theabove-described injection construction, i.e. the heat exchanger may havea first stack containing the passageways containing catalytic material,an adjacent second stack separated from the first stack by anintervening plate with injection holes and a third stack of the coolingor heating construction. The first stack may, for example, lie betweenthe second and third stacks, or they may lie in the order—first, second,third. Needless to say, these three stacks maybe repeated a number oftimes to form the complete heat exchanger/reactor.

[0046] Embodiments of the invention will now be described by way ofexample only with reference to the accompanying drawings in which:

BRIEF DESCRIPTION OF THE FIGURES

[0047]FIG. 1 is a plan view of one slotted plate for use in theinvention;

[0048]FIG. 2 is a plan view in enlarged scale of a portion of a stack ofplates of the type shown in FIG. 1;

[0049]FIG. 3 is an plan view of a portion of another plate for use inthe invention showing the staggering of vents;

[0050]FIG. 4 is a vertical section through a portion of one stack ofplates of the invention;

[0051]FIG. 5 is a similar view to FIG. 4 of a portion of another stackof plates of the invention;

[0052]FIG. 6A is a plan view of an unperforated intervening plate, i.e.a separator plate;

[0053]FIG. 6B is a plan view of a perforated intervening plate, i.e. amixing plate;

[0054]FIG. 7 is a diagrammatic plan view of a modified slotted plate ofthe invention;

[0055]FIG. 8 is a section along line VIII-VIII of FIG. 7;

[0056]FIG. 9 is a perspective view, partly exploded, of a heat exchangerof the invention suitable for use as a catalytic reactor;

[0057]FIG. 10 is a diagrammatic representation of the plate arrangementin the heat exchanger of FIG. 9;

[0058]FIG. 11 is a plan of a stack of three plates used in the heatexchanger of FIG. 9 to provide the passageways for a process fluid toundergo a chemical reaction;

[0059]FIG. 12 is a section on line XII-XII of FIG. 10;

[0060]FIG. 13 is a plan view of a stack of plates used in the heatexchanger of FIG. 9 to provide reactant fluid to be injected into theprocess fluid;

[0061]FIG. 14 is a plan view of another stack of plates similar to theplates of FIG. 13, which stack is used in the heat exchanger of FIG. 9to provide a cooling or heating fluid as required;

[0062]FIG. 15 is a plan view of a separator or intervening plate to liebetween the stacks of FIGS. 13 and 14; and

[0063]FIG. 16 is a plan view of an injection plate to lie between thestacks of FIGS. 11 and 13.

DETAILED DESCRIPTION OF PREFERRED AND ALTERNATE EMBODIMENTS

[0064] In FIG. 1 a rectangular plate 10 for use in the invention has apair of integral side bars 12A and 12B opposed across two sides of theplate.

[0065] Between side bars 12 and 12B extend a plurality of parallel rowsof slots 14, each slot extending entirely through the thickness of theplate and being separated from an adjacent slot in the same row by aland 16. Lands 16 extend continuously across the plate in rows parallelto side bars 12A and 12B. Each slot is separated from an adjacent slotin the next row of slots by a rib 18. Ribs 18 extend in parallel rowsacross the plate between side bars 12A and 12B.

[0066] Each rib 18 is etched to have at least two vents 20 between eachpair of lands 16 or between a land 16 and a side bar 12A or 12B. Thevents extend partway through the rib thickness, i.e. into the plane ofthe paper, and provide communication, i.e. flow channels, between a slotin one row and an adjacent slot in the next row of slots. (Vents areonly shown in one corner region of plate 10 for convenience but it willbe appreciated that they are formed across the whole of the platebetween the side bars.). The vents are shown and described in moredetail with reference to FIGS. 2 to 6 below. The vents 20 enable themain flow passageways for a fluid passing across the plate, when stackedwith one or more identical plates, to be in the direction shown by thearrows A. As the vents in adjacent ribs are staggered, the fluidpassageways extending across the plate, between adjacent parallel lands16 are tortuous.

[0067] The lands 16 are also provide with cross vents 22, again partwaythrough their thickness, to provide cross-flow channels between adjacentpassageways. Again this adds to the turbulence and heat transferproperties. It will be noted that this cross-flow, indicated by arrow B,is through fewer spaced vents so that the main thrust of the flowremains in the general direction indicated by arrow A. It will also benoted that the cross vents are staggered with respect to side vents inadjacent lands.

[0068] In FIG. 2 is shown a stack of four plates 30A, B, C, D, eachsimilar to the type shown in FIG. 1. Each plate has rows of slotsextending between parallel ribs 38A, B, C, D, adjacent slots beingseparated by lands 36A, B, C, D. The slots of each plate stack with theslots of the three other plates to form large slots 34.

[0069] An unperforated boundary plate 40 lies in contact with lowermostslotted plate 30A. Similarly another unperforated plate can lie incontact with uppermost slotted plate 30D whereby fluid passing acrossplates 30A to 30D is confined between the unperforated plates.

[0070] Ribs 38A, B, C, D each have vents 32 etched partway through theirthickness and providing channels for fluid flow between a slot 34 on oneside of the rib and another slot 34 on the other side of the rib. Thesevents thereby provide fluid flow passageways across the plates in thegeneral direction of arrows A. As can be seen, the flow can besinusoidal, from side to side and up and down owing to the staggerednature and the different height of the vents 32.

[0071] Lands 36A, B, C, D are provided with cross vents 33, which arefewer in number than vents 32, but provide flow through the lands in thedirection of arrows B.

[0072] The effect of the staggering of the vents is shown more clearlyin FIG. 3. Here a plate 50 has slots 52 between ribs 54. Each rib 54 hasa plurality of vents 56 etched through its thickness to provide a seriesof rib blocks 54A, the vents providing flow channels between adjacentslots 52. Because the vents in one rib are staggered from those inadjacent ribs, fluid flow across the plate, as indicted by the arrows,is necessarily tortuous.

[0073] As indicated above, the plate may have a coating of catalyst onits surfaces and the coating may form a thick deposit in slots 52 up toa level with the base surface of coated vents 56. This can convenientlybe achieved in the manufactured structure by passing the catalyticmaterial through the structure in known manner to achieve the deposits.In particular the structure may comprise single slotted plate layersbetween pairs of separator plates or pair of slotted plates one invertedon top of the other with their rib blocks 54A in contact, each pairlying between a pair of separator plates. In the latter instance, thecatalyst material may be passed through the structure to leave thedeposits in the slots of one plate and the structure then inverted toreceive more of the catalytic material, which will then deposit in theslots of the second plate of each pair of slotted plates.

[0074] In FIGS. 4 and 5 are shown two stacks of plates of the inventionto illustrate possible variations in the siting of the vents.

[0075] In FIG. 4 are shown four identical slotted plates 60 stackedbetween a pair of unperforated boundary plates 62, 64. Each plate 60 hasvents 66 etched into its face 60A and vents 68 etched into its oppositeface 60B. Vents 66 and vents 68 are staggered from each other along therib of the plate.

[0076] Regions 70 of each plate indicate a land and it will beappreciated that this pattern of vented ribs between adjacent lands isrepeated across the plate as indicated in FIG. 1 along its entirelength.

[0077] In FIG. 5 the unperforated plates corresponding to plates 62 and64 of FIG. 4 have been removed. Again four slotted plates are stackedtogether. The plates, 72A, B, C and D, are identical but alternateplates have been turned over. Thus each plate has in its rib regionthree slots 74 on one face and two slots 76 on the other face. Plate 72Ahas its three slots 74 uppermost and its two slots 76 lowermost. Plate72B has its two slots 76 uppermost and in correspondence with the twoslots 76 of plate 72A. Its lowermost slots 74 are in correspondence withslots 74 of plate 72C. Similarly slots 76 of plate 72C, being lowermost,are in correspondence with the slots 76 of plate 72D. By this meanslarger vent channels are provided through the ribs.

[0078]FIG. 6A shows a single unperforated boundary plate TS that can beused to separate the flow passageways through one group of mainperforated plates from the flow passageways of another group of mainperforated plates.

[0079]FIG. 6B shows a single boundary mixing plate TP. Plate TP hasgroups of circular holes TPP through its thickness, although it will beappreciated that holes of different shape, size and groupings may beused. When plate TP is used as a boundary plate between two groups ofmain perforated plates, a first fluid flow across one group at higherpressure than a second fluid flowing across the other group will beinjected into the second fluid at a controlled rate.

[0080] In FIGS. 7 and 8 is shown plate 80 having a series of squareslots 82 etched or otherwise formed through its thickness. Slots 82extend in rows across the plate, eight rows being shown. Betweenadjacent slots are channels provided by main vents 84 formed partwaythrough the thickness of the plate and cross-channels provided bycross-vents 86 also formed partway through the thickness of the plate.

[0081] The four rows of slots in the right hand half of the plate extendfrom edge 80A to opposite edge 80C of the plate and are fed from aninlet I at edge 80A, fluid being injected into the slots via edge vents841. The fluid can cross towards edge 80C via vents 84, with some of thefluid moving to a different row of slots via the cross-vents 86.

[0082] Fluid flow is indicated generally by the arrows.

[0083] Fluid reaching the slots 82 nearest to edge 80C of the plate isforced to use one or more cross vents 86 and thereby to cross over toone of the four rows of slots extending in the left hand half of theplate. The fluid then travels back from edge 80C to edge 80A of theplate where it exits through outlet O formed by the edge vents 84′.

[0084] A second or further fluids may be injected into the fluid passingacross the plate by means of side injection vents 88, 90 and 92 in edges80B, 80C and 80D respectively of the plate.

[0085] It will be appreciated that these injection vents will beprovided with a one-way valve or other e.g. pressure differential means,to prevent fluid flowing across the plate from exiting through thesevents.

[0086] The injection vents may be positioned to achieve the optimumperformance from the injected fluids(s). It will be noted that each slot82 adjacent an edge of the plate is provided either with an injectionvent to the j edge of the plate or with a blind vent 94. These blindvents may be readily converted to full vents so that a wide range ofinjection patterns is possible.

[0087] It will be appreciated that the vents and cross vents in FIG. 7are shown in simplified form for clarity and that two or more vents maybe provided between each adjacent pair of slots and that thecross-sectional areas of the vents and their numbers may be variedacross the plate to achieve desired flow characteristics.

[0088] In FIG. 9 a heat exchanger/catalytic reactor 100 has an inlet 101and an outlet 102 for coolant (or if required a heating fluid toinitiate an endothermic reaction) and an inlet 103 and an outlet 104 fora reactant fluid which is to be injected as described in greater detailbelow into a process fluid which passes through the open-throughpassageways 105 through reactor 100 in the direction of arrow A. Theinlets and outlets lead into and out of tanks 110 and 111 respectivelyfrom which the fluids are fed into their appropriate stacks.

[0089] Reactor 100 will of course be connected in a fluid-tight mannerto a pipeline (not shown) or other means of passing the process streamfrom a source, through the reactor 1000 to a suitable receiving vesselby conventional means. Such connection may conveniently be made bybolting flanges 100A and 100B at either end of reactor 100 tocorresponding flanges provided in the pipeline or other means using boltholes 100C.

[0090] The passageway or channels 105 are defined in stacks of plates tobe described with reference to FIGS. 11 and 12 below. These channels maybe packed with catalyst and, after a period of use, the reactor 100 maybe readily unbolted from its pipeline, the spent catalyst removed fromchannels 105 and fresh catalyst inserted so that the reactor is readyfor re-use.

[0091] A mesh 105A mounted in a frame 105B can be clamped to frame 100Band/or 100A to retain the catalyst in the passageways 105.

[0092] The order or arrangement of the plates in the reactor 100 isshown in FIG. 10.

[0093] At each end of the total stack of plates is a solid unperforatedplate S, which is described with reference to FIG. 15 below.

[0094] Above bottom plate S in FIG. 10 is a stack A of plates definingpassageways to receive the coolant (or heating) stream through inlet101. The plates of stack A are described with reference to FIG. 14below.

[0095] Above stack A is another solid unperforated separator plate S.Above that plate S is a stack of plates B defining passageways toreceive a reactant fluid. The plates of stack B are described withreference to FIG. 13 below.

[0096] Above stack B is an injection or mixing plate I, which isdescribed with reference to FIG. 16 below.

[0097] Above injection plate I is a stack C of plates defining thepassageways 105 referred to above for the process fluid. The plates ofstack C are described below with reference to FIGS. 11 and 12.

[0098] Above stack C is another solid, unperforated separator plate S.

[0099] This structure may then be repeated with another stack A and soon as many times as is required to build up heat exchanger/reactor 100to the desired capacity.

[0100] A separator plate is shown in FIG. 15. It has a rectangular planform where border region 156 can be bonded to the corresponding borderregions of adjacent plates by one of the means discussed above. Borderregion 156 encloses and merges into an unperforated, i.e. solid, centralregion 157 which prevents fluid flow passing from one side of plate S toits other side. Adjacent each comer of the plate S is a loop extension158 defining an enclosed region or aperture 159. These loops 158 stacktogether with corresponding portions of the other plates stacked in theheat exchanger to form two inlet and two outlet tanks 110 and 111respectively, one of each being visible in FIG. 9.

[0101] The top plate of stack A is shown in FIG. 14. Two or more suchplates 170 are required and each is of a rectangular form having aborder region 171 for bonding to adjacent plates and a central region172. Region 172 is of vented rib construction—not shown here but, forexample, as shown in FIGS. 1 to 3. As with plate S, adjacent the comersof plate 170 are loops, two of which, 173A and 173B, in opposite comers,enclose an aperture 174 and the other two of which 173C, 173D, open intocentral region 172, thereby providing entry and exit for coolant fluidpassing across and through stack A via inlet 101 and outlet 102 shown inFIG. 9.

[0102] The top plate of stack B is shown in FIG. 13. Two or more suchplates 180 are required and they are of identical structure to plates170. Thus they have a border region 181 enclosing a central pin-finregion 182. They have enclosed loops 183A and 183B and loops 183C and183D, the latter two loops providing an inlet and an outlet for reactantfluid to pass across and through stack B via inlet 103 and outlet 104 ofFIG. 9.

[0103] Injector plate I is shown in FIG. 16. It is of the samerectangular form as the plates described above. Its border region 191can be bonded to the border regions of adjacent plates and it enclosesand merges into a central region 192. Region 192 is not imperforate buthas a series of injection holes 190 passing through its thickness. Thusreactant fluid passing through stack B on one side of plate I can bearranged to be at higher pressure than process fluid passing throughstack C on the other side of plate I, whereby the reactant fluid will beinjected through holes 190 into the process fluid to cause the desiredchemical reaction. Holes 190 can be of size and distribution to suit therequired amount of reactant fluid to be injected.

[0104] As with the previously described plates, plate I has comer loops193A, B, C, D, and each loop encloses an aperture 194 to form part ofthe tanks 110 and 111 shown in FIG. 9.

[0105] The plates 120 of stack C are shown in FIGS. 11 and 12. Threeplates are shown in this stack although it will be appreciated that moreor less plates may be used, as desired. Again, plates 120 arerectangular with a border region 121 along their two longer edges.Border regions 121A, 121B along their shorter edges are designed to beremoved by cutting along lines XII-XII and XI-XI after the plates havebeen bonded to the other plates in the heat exchanger.

[0106] Central region 122 of each plate 120 has a series of parallelribs 123 running along its longer length. Between adjacent pairs of ribs123 and between each outermost rib 123 and border region 121 lie openchannels 124, (equivalent to channels 105 in FIG. 9). The channelsextend completely through the thickness of the plate. When ends 121A and121B are removed process fluid can pass from one side of stack C, whereends 121B were, along channels 124 and out at the other end, i.e. whereends 121A were, as indicated by arrows A. Arrows A here correspond toarrow A in FIG. 9.

[0107] It will be appreciated that ribs 123 are held in their positionsinitially by being joined to ends 121A and 121B of plate 120. When theplates of the stacks are bonded together, ribs 123 bond to a plate Ibelow or plate S above (as in the arrangement shown in FIG. 10) or tothe corresponding ribs of adjacent plates 120. Thus when ends 121A and121B are removed, the ribs remain firmly in place.

[0108] Channels 124 may be packed with catalyst to promote the reactionbetween the process fluid passing across and through stack A with theinjected reactant fluid for stack B.

[0109] If it is desired to equalise pressure between the catalystchannels 124, vents may be formed partway through the thickness of ribs123. Moreover, all the channels 124 in a plate 120 need not be of thesame width. By this means, different flow rates may be promoted indifferent channels or poor uniformity of flow distribution through thechannels may be compensated for by having wider channels at the edges ofthe plate.

[0110] Plates 122 each have comer loops 125A, B, C, D, completelyenclosing apertures 126, to form part of the tanks 110 and 111.

[0111] By way of example only, plates 120 may be about 2 mm in thicknessand the requisite number of such plates will be stacked together to givethe desired channel height.

1. A heat exchanger or fluid mixing means comprising a bonded stack ofplates, the stack comprising at least one group of plates, comprisingone or more perforated plates (50) sandwiched between a pair of primaryseparator plates, each perforated plate has a plurality of perforationsarranged in rows across the plate in a first direction, with a landbetween each adjacent pair of perforations in a row and with ribs (54)between adjacent rows, the lands forming barriers to flow in the firstdirection across the plate and the ribs forming barriers to flow in asecond direction across the plate, the second direction being normal tothe first direction, the ribs (54) having vents (56) through a portionof their thickness, the vents extending from one side of a rib to theother side in the second direction, whereby flow channels are providedthrough the vents and the flow channels defined by the perforationslying between each adjacent pair of lands provide a flow passage tocross the plates in the second direction, wherein a deposit of catalyticmaterial is retained within the passageways of the said at least onegroup of plates.
 2. A heat exchanger or fluid mixing means comprising abonded stack of plates, the stack comprising at least one group ofplates, comprising one or more perforated plates (50) sandwiched betweena pair of primary separator plates, each perforated plate has aplurality of perforations arranged in rows across the plate in a firstdirection, with a land between each adjacent pair of perforations in arow and with ribs (54) between adjacent rows, the lands forming barriersto flow in the first direction across the plate and the ribs formingbarriers to flow in a second direction across the plate, the seconddirection being normal to the first direction, the ribs (54) havingvents (56) through a portion of their thickness, the vents (56)extending from one side of a rib (54) to the other side in the seconddirection, whereby flow channels are provided through the vents (56) andthe flow channels defined by the perforations lying between eachadjacent pair of lands provide a flow passage to cross the plates in thesecond direction, wherein the deposit of catalytic material is formed inthe perforations of the perforated plate(s).
 3. A heat exchanger orfluid mixing means according to claim 2, wherein the perforations of theperforated plates are elongate slots (52).
 4. A heat exchanger or fluidmixing means according to claim 3, wherein the vent has a base surfaceand the deposit is formed in the slots (52) to a level with said basesurface.
 5. A heat exchanger or fluid mixing means according to claim 2,characterised in that the vents (56) are formed on one surface of theirrib (54) to extend partially into the thickness of the rib (54).
 6. Aheat exchanger or fluid mixing means according to claim 5, wherein thevents (56) in adjacent pairs of ribs (54) are offset from each other. 7.A heat exchanger or fluid mixing means according to claim 6,characterised in that the vents (56) are formed normal to the directionof the rib (54).
 8. A fluid mixing means comprising a bonded stack ofplates, the stack comprising in series a plurality of passageways for afirst coolant or heating fluid stream, one or more first perforatedplates (170) for providing a plurality of passageways to receive areactant fluid, one or more second perforated plates (120) for providinga plurality of passageways (105, 124) in which catalytic material ispacked to receive a process fluid and a plurality of passageways for asecond coolant or heating fluid whereby the reactant fluid passagewaysand process fluid passageways are connected thereby to mix the reactantfluid and process fluid in the presence of a catalyst and in temperaturecontrolled conditions.
 9. A fluid mixing means according to claim 11,wherein the passageways (105, 124) formed by the second perforated platerun through the fluid mixing means and are accessible to enable thecatalyst to be packed in the passageways and removed when required. 10.A fluid mixing means according to claim 9, wherein the perforations ofthe second perforated plates (12) are elongate slots and the catalyticmaterial are packed in the slots.
 11. A fluid mixing means according toclaim 9, characterised in that the passageways (105,124) to containcatalytic material are defined in one or more plates (120) and liebetween parallel ribs (123) running the length of those plates (120).12. A fluid mixing means according to claim 8, characterised in thatvents are formed partway through the thickness of the parallel ribs toprovide pressure equalising means between the passageways (105, 124) tocontain catalytic material.
 13. A fluid mixing means according to claim8, wherein the passageways for first and second coolant or heating fluidstreams are provided by one or more third perforated plates (170)comprising a border region for bonding adjacent plates and a centralregion having a plurality of vented ribs defining passageways forcoolant fluid or heating streams.
 14. A fluid mixing means according toclaim 13, wherein the third perforated plates (170) are provided with acentral pin-fin region.
 15. A fluid mixing means as claimed in claim 13,wherein the first and second perforated plates (170, 120) are separatedby an injection plate (I) having a series of injection holes 190,whereby the reactant fluid is caused to be injected into the processfluid to cause the desired chemical reaction.
 16. A fluid mixing meansaccording to claim 15, wherein the second and third perforated platesand the injector plate (I) are provided at their edges with extensions(173, 183, 193) which fit together in the stack to provide one or moretanks on the side faces of the stack.
 17. A fluid mixing means accordingto claim 8, wherein the first perforated plates (170) are provided witha central pin-fin region.
 18. A fluid mixing means comprising a bondedgroup of plates which group of plates comprise in series, a firstseparator plate (S), a stack (A) of first perforated plates forproviding a plurality of passages for a coolant or heating fluid stream,a second separator plate (S), a stack of second perforated plates forproviding a plurality of passages to receive a reactant fluid, aninjection plate (I), and a stack (C) of third perforated plates forproviding a plurality of passageways for a process fluid, and a thirdseparator plates, whereby the reactant fluid is caused to be injectedinto the process fluid to be mixed in the presence of a catalystcontained in the stack (C) of the third perforated plates.